At the very least they need to make it reset on death, or no one is going to use it.

It does.

To say a bit more on the 7.1.5 changes to various “cheat death” effects, including Cheat Death, Cauterize, Purgatory, and Last Resort: firstly, the cooldown increase is not the only change—the cooldowns (specifically, the cooldown-enforcing debuffs) will now clear on death. So if you Cheat Death early in a dungeon, yes, you should avoid dying again for the next 6 minutes. However, in the event you do die (or the group wipes), you will return to combat with Cheat Death once again available.

More broadly, we examined the value of these effects as a whole and concluded they are too easily available. When Cheat Death was first added as a deep Subtlety talent (before the change to modern talent rows), its power and cooldown reflected the significant investment into that tree. In the current game, not only is its opportunity cost much lower, but, taking a look at the gameplay of healing and survivability challenges, the power level of such a frequent extra life is very high. For example, Rebirth has a 10 minute cooldown, and is a distinctively powerful ability that significantly contributes to a class’s perceived power in dungeons. Reincarnation has a 30 minute cooldown, and is far from being meaningless or forgotten. If we were adding Cheat Death and its ilk today and evaluating its power, there would be little justification for a cooldown as short as 2 minutes. Preventing a death that might otherwise have scuttled the entire current attempt at a dungeon or raid boss has more value than that.

On Last Resort in particular, we are aware that Vengeance Demon Hunters felt somewhat reliant on this to avoid deaths to unexpected burst damage, and we will be monitoring whether they need other changes to compensate (for example, they have increased health on PTR, increased baseline damage reduction, and a stronger Metamorphosis effect). And on Purgatory, its cooldown was increased the least because it conditional, and it was also made more reliable: the effect will now always last for 3 seconds regardless of whether you momentarily go above 0 HP during that window.